1. FIELD OF THE INVENTION
This invention relates to a heat exchanger, and more particularly it is concerned with a heat exchanger of the type having particular utility as a radiator dissipating heat from cooling water for engines of automotive vehicles, for example.
2. DESCRIPTION OF THE PRIOR ART
Generally, conventional radiators for automotive engines are composed of a core unit 4 having metallic tubes 2 and corrugated fins 3 connected with each other by welding in a heat transmitting manner, and an upper and a lower core plate 5 connected to both ends of the tubes 2 by welding, as shown in FIG. 1. Each of the core plates 5 is formed with a holding groove 6 along its periphery.
A soft seal member 7 such as O-ring is held in the holding groove 6, as shown in FIG. 2. And a flange 9 of a plastic tank member 8 is also held in the holding groove 6, so that the seal member 7 is interposed between a bottom wall 5b of the holding groove 6 and the flange 9.
A plurality of hooks 10 integrally formed at equal intervals with an outer side wall 5p of the holding groove 6 are bent inwardly by a jig (not shown) so that the seal member 7 is compressed. Since a distance between a lower surface of the bottom wall 5b of the holding groove 6 and an upper surface of the bent hooks 10 is maintained constant by the jig, the compression ratio of the seal member 7 having a great influence on the seal efficiency between the tank member 8 and the core plate 5 is determined by a thickness h of the flange 9 and a thickness t of the core plate 5.
The heat exchanger is made as follows. The tubes 2 coated with solder on their outer surface, corrugated fins 3 not coated with solder, and core plates 5 coated with solder on their outer surface, are assembled as shown in FIG. 1, and the assembled unit is carried into a furnace in order to melt the solder so as to weld each other. At this time overflow melting solder is gathered around the bottom wall 5b, outer side wall 5p, or hooks 10, as shown in FIG. 1, being in a form of drops 11.
The heat exchanger of this kind, however, has following disadvantages; When the plurality of hooks 10 are bent by the jig, while the drop-shaped mass of the solder remains on those portions, the seal efficiency between the core plate 5 and the tank member 8 by the seal member 7 is deteriorated, because as shown in FIG. 3, there exist some portions where extra (over-flowed) solder 11 is attached and the seal member 7 in those portions are compressed more tightly than other portions. As above, the irregularity of compression ratio of seal member 7 reduces the seal efficiency. And since the portions at which the extra PG,4 solder 11 is attached are stronger than the other portions, the bending force of the jig concentrates on the weak portions, the hooks 10 and the outer side wall 5p of the holding groove 6 of the weak portions are bent more as required, as shown in FIG. 4. This makes a relatively wide gap a between the hooks 10 and the flange 9 as well as a relatively wide gap b between the outer side wall 5p and the flange 9, whereby the wall becomes rugged, which makes the life time of the radiator shorter.